Patent GB-1227698-A (GB)
IPC: G09G1/08
Filed: 1969-06-05
Abstract: 1,227,698. C.R.T. display circuits. SPERRY RAND CORP. 5 June, 1969 [10 June, 1968], No. 28468/69. Heading H4T. In a two-dimensional C.R.T. display circuit for alphanumeric character and/or graphic data wherein a display control operates upon the beam locating circuits of the C.R.T. to display data in a first unexpanded mode upon a first screen area, and to selectively display other data in the first mode or in a second expanded mode in a second screen area; the control comprises an expansion circuit controlling the scale of data display in a selected sector of the second screen area, so that data is displayed in the selected sector in the second mode, while the data in the first area continues to be displayed in the first mode. A cathode-ray tube 42 (Fig. 4) has a screen with upper and lower first areas displaying characters and a second central area displaying graphic vector and/or alphanumeric character data in a normal or expanded mode, and the central area (Fig. 2a) contains plural, e.g. 64 message display addresses designated in X and Y senses by binary coding; the expansible sectors being designated by numerals 1 to 9 and bounded by areas designated by letters A to P (Fig. 2b, not shown); a selected sector in expansion filling the central area. If a data display (Fig. 3a) contains, e.g., vector N, tabular words CAT, MIKE, ABLE, and random characters G, K, X disposed as shown, the beam positioning circuits are controlled to shift the blanked beam successively to the positions of desired characters or component lines, at which the same are displayed, while for a tabular word the blanked beam is controlled to a starting point and successively to points displaced therefrom by fixed increments at which the successive tabular characters are displayed. In expansion display (Fig. 3b) the specifying of random characters G, K, X is expanded proportionally to vector N; the tabular word CAT is unexpanded, the terminal letters of the word MIKE overlapping into the expanded sector 5 are suppressed for clarity, while the initial letters of the word ABLE overlapping out of the expanded sector 5 are retained. The portions 18, 22, 24 of the expanded vector N which would otherwise overlap out of sector 5 into neighbouring sectors is suppressed by blanking the beam at the intersections 16, 20 &c. with the edges of sector 5 (Fig. 3b), and caused to move while blanked over sector 5 in paths 18<SP>1</SP>, 22<SP>1</SP>, 24<SP>1</SP> complementary to the off screen paths (Fig. 3c) until arrival at the intersections in the return direction for re-entry to the expanded sector, at which blanking is removed and the beam continues to describe the vector N. The circuit (Fig. 4) which is duplicated for axes X and Y, comprises a processor 40 generating digital character signals on line 44, digital X (or Y) vector component on line 46 and control signals on line 48, with data storage, buffer storage, and display control circuitry. Vector signals initiate display of a vector of the beam if unblanked, or translate the blanked beam to a vector starting point or a specific character display location; after which signals on line 44. drive character generator 50 (which may be of the kind described in Specification 1,108,401) to generate the required character. Vector signals on line 46 are applied to a normalizing circuit, examining the input component and deriving segmental signals added in sequence to deflect the beam position to derive the required vector; the component data being shifted along a storage register during examination. An arithmetic circuit 56 is provided comprising an adder, and an output register and D/A converter 58 to provide signals on line 60 to the display deflection circuitry. A character spacing unit 62 operates under control of selected input control flip-flops 64 indicating character size and character display over line 66, to supply a spacing movement signal to arithmetic circuit 56, whose output is operated upon by output -gating circuit 70 to alter the value applied to the output register and D/A converter 58. A sector selector 72 is coupled to 10 push-button switches individually applying actuating voltages, of which 1 to 9 are mutually exclusively operable and select a sector for expansion, while 10 selects non-expansion, and energizes line 74 to expansion override circuit 76; receiving plural control signals over line 79 from input control flip-flops 64 to provide a normal signal on line 77. Plural control signals from input control flip-flops 64 over line 79 are applied to expansion override circuit 76, while the normal signals on 74, 77 are removed in operation of expansion switches 1 to 9, and an expand signal on 78 is applied to control blanking circuit 80, character spacing circuit 62, and AND circuit 82 which when enabled provides control signal for horizontal output register and D/A converter 58 shifting the addressing data signals a predetermined amount for expansion. Sector selector 72 controls blanking decoder 88 over line 86, whose signals are compared with signals over 90 from output gating circuit 70 representing the two highest ordered bits therein, to produce signals at 92 indicating when the beam position represented by the data in 70, is out of the area selected for display by 72. Thus blanking circuit 80 blanks the beam of display 42, and the signal on 92 is applied to AND gate 82, whereby a signal is produced on line 84 when the circuit is set to EXPAND and the beam is positioned out of the required sector, and causes the beam deflection signals to be complemented and the blanked beam to be moved on-screen within the expansion sector, until it reaches the position of re-entry from an off-screen path. When display is expanded, and controlled to display characters in an upper or lower area; processor 40 signals flip-flops 64 over line 48 to provide control signals over line 79 to expansion override circuit 70, which in turn overrides the expand signal on line 78 by its output on line 77, whereby a normal output signal appears. An input control flip-flop 64 produces signal on line 96 to the arithmetic circuit 56 indicating positioning of the electron beam, which enables addressing data on lines 46, 46<SP>1</SP> to pass direct to arithmetic circuit 56; by-passing normalizing circuit 54 and character-spacing circuit 62. The addressing data forces the blanked electron beam to its specified starting position, and represents the position in an upper or lower area to which it is to move, and is coupled directly over gating circuit 70 due to presence of normal gating signal over line 77. Display 42 is then conditioned to display either tabular or random characters. The rest control signal on line 48 sets the appropriate flip-flops 64 so that signal on line 66 indicates character display, which with normal signal on line 77 coupled to character spacing circuit 62 causes a set of digital data values representing character spacing to be coupled to arithmetic circuit 56 and added to present beam position. Character signals are then connected over line 44 to character generator 50 displaying the appropriate character. For tabular characters, the spacing and display sequence is repeated until a control signal indicates completion of tabular character sequence. Detailed logic circuits are described (Figs. 5a, 5b, 5c, not shown).